Mixture for supplying a boiler or a diesel engine, comprising diesel fuel or heating oil and esters and alkanes from the transformation of biomass

ABSTRACT

The goal of the invention is a mixture of liquid fuels for boilers or diesel engines with particular chain length esters and alkanes, and use thereof for reducing particle and nitrogen oxide emissions during operation of the boilers or diesel engines.

TECHNICAL FIELD

The present invention relates to a mixture of liquid fuels for boiler or diesel engine, comprising specific compounds which reduce particle and nitrogen oxide emissions from boilers and diesel engines during their operation.

BACKGROUND SECTION

From the perspective of fighting greenhouse gases, diesel engines are effective engines because, at equivalent power, they emit about 20% less greenhouse gases than gasoline engines. Just the same they are increasingly criticized because of certain emissions harmful to people, in particular particle and nitrogen oxide emissions. In some major urban centers, even some entire regions, air pollution from these emissions constitutes a major problem.

In many countries, particle and nitrogen oxide emissions from diesel engines are regulated. This is notably the case in Europe where the limits set by regulations are increasingly strict (Euro6 standards currently). This is also the case in other major countries, in particular the United States, but with very low limits in some states such as those set by the California Air Resources Board.

Particles are subject to two categories of measurements:

-   -   Measurements which characterize the color of the exhaust gas         (smoke measurements); and     -   Measurements of particle weight, diameter and count.

Particle sizes are varied. Generally, four categories of small particles are recognized: PM₁₀ with a diameter under 10 μm, PM_(2.5) with a diameter under 2.5 μm, ultrafine particles with a diameter under 0.1 μm and nanoparticles characterized by a diameter under 50 nm.

Most particles emitted from diesel engines have a diameter under 1 μm. They therefore represent a mixture of fine or ultrafine particles and nanoparticles. The smallest are considered the most dangerous for humans.

For 30 years diesel engines have made remarkable progress through the improvement of the quality of fuels (reduction of sulfur content), of the combustion process (optimization of injection systems) and in the methods for exhaust gas treatment (e.g. exhaust gas recirculation, catalytic oxidation systems and particle filters). Despite a reduction of particle emissions from new engines of order 98% over some 30 years, the problem of particles is seen as sufficiently serious that some urban centers have reached the point that they want to ban diesel vehicles in the city. This is due in particular to the fact that diesel vehicles are kept for many years (8 to 10 years for personal vehicles and often over 15 years for trucks and buses).

In addition to emission reduction measures on new vehicles and the promotion of alternative energies (e.g. electric vehicles or natural gas vehicles), it would be very useful to find solutions for existing diesel engine vehicles.

The same problems with particle and nitrogen oxide emission are encountered with liquid fuels for boilers, in particular with old boilers for which the contribution to particle and nitrogen oxides pollution is also very significant.

SUMMARY

The goal of the present invention is to address these problems and in particular to provide a simple, effective and economical solution for reduction of emissions from diesel engines and liquid fuel boilers.

For that purpose the invention proposes to incorporate in the diesel engine fuel or the boiler fuel one or more specific esters and one or more specific alkanes together, in addition to those which could already be present in the fuel.

Before the 1990s, biofuels for diesel engines did not exist whereas ethanol had been used in gasoline for a long time, in particular in Brazil and the United States.

Starting around 1992, the use of biodiesel, which is a methyl (or ethyl) ester of vegetable oil, started to be developed in France, and then in Europe and in the world. Today, various types of esters are used depending on the origin of the fats which are transesterified by an alcohol: vegetable oils, animal fats or recovered fryer oils. It involves esters of fatty acids where the length of the chain is primarily included between 16 and 18 carbon atoms. These products are generally incorporated in ordinary diesel fuel at a level below 8% or else they are used at 20% or 30% or, as an exception, pure in captive transport fleets. But the improvements that can be achieved in the area of particle reduction with such mixtures are limited (reduction of the order of half the rate of incorporation of esters). Further, these esters tend to increase the nitrogen oxides. They are subject to the European standard EN14214 and to similar standards, elsewhere in the world, and the rate of incorporation in ordinary diesel fuel is generally limited to 8% by volume, in particular for this reason.

Other biofuels, in particular alkanes from biomass, are starting to be developed, whether they are vegetable oils or hydrotreated animal fats (treated with hydrogen to eliminate oxygen atoms) which also have 16 to 18 carbon atoms or else BTL (Biomass to Liquid) type products from biomass gasification followed by Fischer-Tropsch synthesis. Other solutions were developed, still experimentally, such as hydrotreated oils from pyrolysis and alkanes which can be obtained by anaerobic fermentation of biomass followed by Kolbe electrolysis (patent application WO 2014/170603).

These hydrocarbons are interesting because in general they have a high cetane number which supports a reduction of NOx emissions. However the effect on particles remains limited.

Further, the addition of various oxygenated compounds (e.g. alcohols or esters) to fuels has been proposed for several years—for goals that were not reduction of particle emissions, but the improvement of other functions (e.g. improvement of cold resistance, lubricating power, impact on agriculture, impact on greenhouse effect, etc.), for example:

-   -   The use of over 10% ethanol in diesel fuel but this requires the         presence of costly additives;     -   The incorporation of butanol in diesel fuel (for example: Energy         Conservation and Management Vol 51, Issue 10, October 2010,         Effects of butanol-diesel fuel blends on the performance and         emissions of a high-speed DI diesel engine);     -   The incorporation in gasoline, diesel fuel or kerosene of esters         coming from anaerobic fermentation of biomass (patent FR         2,757,539A1, Dupré-Kaplan, Use of esters as fuels or         combustibles).

Tests have also been done on the use of aldehydes in diesel fuel (Reducing the Emission of Particles from a Diesel Engine by Adding an Oxygenate to the Fuel Environmental Science and Technology 39(16):6260-5⋅September 2005) with an objective of reducing emitted particles, but the emissions of acetaldehyde, which is also thought to be dangerous, were greatly increased.

Nonetheless, none of these solutions led to a satisfactory solution with which to reduce particle emissions and nitrogen oxide emissions during operation of boilers and diesel engines.

The present invention specifically targets the incorporation in diesel fuels or liquid fuels for boilers chosen among diesel fuel and home heating oil:

-   -   At least one biosourced ester where the chain length is included         between 8 and 14 carbon atoms; and     -   At least one biosourced alkane where the chain length is         included between 8 and 14 carbon atoms.

Where the ester(s) with a chain length included between 8 and 14 carbon atoms incorporated in the fuel represented between 1% and 80% by volume of said mixture and where the alkane(s) with a chain length included between 8 and 14 carbon atoms incorporated in the fuel represent between 1% and 80% by volume of said mixture.

In the meaning of the invention, biosourced is understood to mean products coming from biomass, meaning agricultural or forest plants or organic waste.

It should be noted that biosourced esters and alkanes can be distinguished from esters and alkanes of petroleum origin present in a mixture because of dating based on mass spectrometer measurement of the proportion of the C14 isotope relative to all the carbon in the molecule. Fossil products have a smaller C14 concentration than products resulting from more recent photosynthesis.

While the esters are going to lower the particle emissions, it is important according to the invention to add alkanes with chain lengths included between 8 and 14 carbon atoms in addition to those which could already be present in the fuel, because an increase of the nitrogen oxide emission can be avoided that way.

The mixture according to the invention is a liquid mixture which has a variable composition. Advantageously, particle and nitrogen oxide emissions during operation of boilers and diesel engines can be reduced with such a mixture without the worsening of other emissions (e.g. nitrogen monoxide, CO, unburned hydrocarbons, HC, etc.). Also, with the invention the mixture can be made such that it meets all the specifications for liquid fuels, in particular, those which are the most difficult to meet, specifically: the flashpoint must be above 55° C. and the calculated cetane number which must be over 46. Further, the properties of the diesel engine fuel or liquid fuel for boilers—such as for example cold resistance, viscosity, etc.—can be retained with the mixture according to the invention.

The esters and/or alkanes used can in particular be biosourced, meaning be biofuels coming from agricultural or forest biomass or form organic waste, which also has an advantage for combatting the greenhouse gas effect.

DETAILED DESCRIPTION

The invention therefore aims for a mixture intended to supply a boiler or diesel engine, comprising:

-   -   at least one liquid fuel for boiler or diesel engine fuel chosen         among diesel fuel and domestic fuel oil; and         -   At least one biosourced ester where the chain length is             included between 8 and 14 carbon atoms incorporated in the             fuel; and         -   At least one biosourced alkane where the chain length is             included between 8 and 14 carbon atoms, incorporated in the             fuel;

Where the incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture, preferably between 5 and 50%, and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture, preferably between 5 and 50%.

The incorporated ester(s) with chain length included between 8 and 14 carbon atoms present in the mixture can be chosen among any ester with this size. It can preferably involve ethyl hexanoate (C8), butyl butyrate (C8), butyl valerate (C9), butyl hexanoate (C12) and/or butyl caprylate (C14). Preferably, it does not involve esters of higher fatty alcohols, meaning alcohols obtained from vegetable oil fatty acids that were reduced for example by hydrogenation and that are combined with a short acid such as formic acid or acetic acid.

The incorporated alkane(s) with chain length included between 8 and 14 carbon atoms present in the mixture can be chosen among the alkanes with this size (branched or unbranched). It can preferably involve decane, dodecane and tetradecane.

According to the invention, by specifically selecting esters with a chain length included between 8 and 14 carbon atoms, it will advantageously be possible to continue meeting all current specifications for diesel engine fuel and boiler fuel, including at an incorporation level between 1 and 8%, except for the maximum level of esters because the esters produced that way are not the methyl esters of fatty acids meeting the standard EN14214. Thus, according to a variant, the invention targets the mixture such as previously described in which the ester(s) with chain length included between 8 and 14 carbon atoms represent between 1% and 8% of the volume of said mixture. This mixture can be dispensed as an ordinary fuel in all distribution pumps.

Further, the esters used according to the invention can also be used at higher levels. Thus, according to another variant, the invention targets the mixture such as previously described in which the incorporated ester(s) with chain length included between 8 and 14 carbon atoms represent between 8% and 80% of the volume of said mixture, which will be distributed either as an ordinary fuel if it is approved for that use, or as a fuel for captive transport fleets.

Preferably, the ester(s) with chain length included between 8 and 14 carbon atoms present in the mixture are esters of biosourced origin obtained from volatile fatty acids coming from anaerobic biomass fermentation and esterification by an alcohol.

Likewise, a mixture is preferred in which the incorporated alkane(s) with chain length included between 8 and 14 carbon atoms present in the mixture are alkanes obtained by Kolbe electrolysis of volatile fatty acids coming from anaerobic fermentation of the biomass such as described in the application WO2014/170603 or from the biomass by gasification and Fischer-Tropsch synthesis.

The mixture according to the invention, in addition to the fuel, esters and alkanes of specific chain length, could contain at least one additional additive for improving the cetane number and/or increasing the reduction of particle emissions and/or reducing nitrogen oxide emissions by the boiler or diesel engine during operation thereof. It can involve for example tetranitromethane.

Other additives can be added to improve other functionalities of the mixture like cold resistance, viscosity, etc.

The mixture according to the invention can be obtained by other conventional techniques of the person skilled in the art. Preferably, it is obtained by a simple mixing of the constituents in a single tank or the mixing of two fluids in a single pipe. In most countries, such a mixing would have to be done under the control of the Customs Department.

The invention specifically targets a process for production of a mixture according to the invention such as previously described, which consists of incorporating in at least one liquid boiler fuel or diesel engine fuel chosen among diesel fuel or domestic fuel oil:

-   -   At least one biosourced ester where the chain length is included         between 8 and 14 carbon atoms; and     -   At least one biosourced alkane where the chain length is         included between 8 and 14 carbon atoms.

In a way that the incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture.

Preferably, the mixing is done at a temperature included between 10 and 50° C. in a stirred tank or in a device where the various components are mixed by crossflow mixing.

Surprisingly and advantageously, with the mixture according to the invention, which incorporates specific esters and alkanes in diesel engine fuels or in boiler fuels, a very significant reduction of particle emissions is possible without a worsening of other emissions in particular nitrogen oxides and other emissions such as CO, HC, etc. The level of reduction of the particles by mass and count is of order twice the rate of incorporation (30% to 40% for 20% incorporation; 60% to 80% for 40% incorporation; and 80% to 90% for 50% incorporation), which constitutes a considerable advantage for reducing particle emissions in cities. Since there is a parallel reduction for particle mass and count, this process does not enhance smaller particles which are more dangerous.

The invention therefore specifically targets the use for supplying a boiler or diesel engine with a mixture comprising:

-   -   At least one liquid fuel for boiler or a diesel engine fuel         chosen among diesel fuel or domestic fuel oil; and     -   At least one biosourced ester where the chain length is included         between 8 and 14 carbon atoms incorporated in the fuel; and     -   At least one biosourced alkane where the chain length is         included between 8 and 14 carbon atoms, incorporated in the         fuel;

The incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture.

In particular, the invention targets the use of the mixture in a boiler or diesel engine for reducing the particle emissions and/or reducing the nitrogen oxide emissions during operation thereof. Advantageously, the cetane number of the fuel can also be improved with the invention.

The mixture according to the invention can be used in any liquid fuel boiler and in any diesel engine, in particular in a fixed diesel engine or diesel engine installed in transportation vehicles or boats or worksite heavy equipment or agricultural equipment or small domestic equipment such as lawnmowers or rototillers.

In addition to the mixture according to the invention, at least one additive can be added in the boiler and/or the engine, where the additive is capable of improving the cetane number and/or improving the reduction of particle emissions and/or reducing the nitrogen oxide emissions by the boiler or the diesel engine during operation thereof, and/or at least one additive capable of improving other functions of the mixture like cold resistance, viscosity, etc.

Examples 1-5

The invention is now illustrated by examples of mixtures according to the invention and emission test results on an engine test bench showing their effectiveness.

The composition of the various mixtures tested is described in the table (examples 1 to 5 with various load rates which represent the number of RPMs of the engine compared to the nominal number of revolutions). These mixtures are obtained by simple mixing of components in jugs with manual agitation.

The measurements are done at the exhaust of a Renault brand car engine by a Horiba 9100 (CO, CO2, O2, HC and NOx) and PPS PEGASOR particle analyzer.

The results obtained are shown in the following table:

Fuel % load mg/m3 N/cm3 Smoke CO NOx Reference diesel 20 3.9 19,000 0.3 700 85 30 34 170,000 2.8 810 116 40 43 220,000 3.9 1600 238 45 20 95,000 2 830 370 60 1.5 7,000 0.4 220 1300 EXAMPLE 1: INVENTION 20 3.6 18,000 0.25 764 63 Diesel + 10% decane + 20% butyl butyrate 30 13 62,000 1.35 540 114 Substantial drop of particles (−31% by 40 9 42,000 0.92 343 331 count) 45 7 32,000 0.75 350 575 Without substantial worsening of NOx 60 1.8 8,500 0.23 475 1214 EXAMPLE 2: INVENTION 20 2.3 11,000 0.17 800 55 Diesel + 20% decane + 20% butyl 30 15 70,000 1.65 575 100 hexanoate 40 19 88,000 2.2 920 222 Substantial drop of particles (−48% by 45 18.5 90,000 2.35 880 235 count) 60 1.3 6,000 0.29 270 1168 Slight drop (−15%) of NOx EXAMPLE 3: INVENTION 20 3.2 15,000 0.23 870 41 Diesel + 20% decane + 20% butyl butyrate 30 15.5 74,000 1.6 591 92 Substantial drop of particles (−36% by 40 31 148,000 3.5 1806 160 count) 45 19 82,000 2.12 960 240 Slight drop (−19%) of NOx 60 1.5 6,800 0.32 465 1186 EXAMPLE 4: INVENTION 20 0.3 1,600 0.03 1240 72 30% diesel + 20% decane + 50% butyl 30 3 14,000 0.22 530 122 butyrate 40 5 23,000 0.34 337 228 Large drop of particles (−88% by count) 45 4.5 21,000 0.42 347 300 Slight drop (−11%) of NOx EXAMPLE 5: INVENTION 20 1 5,000 0.04 1218 50 ⅓ diesel + ⅓ decane + ⅓ butyl 30 5.5 28,000 0.41 550 101 butyrate 40 13 62,000 1.00 566 182 Large drop of particles (−74% by count) 45 7 35,000 0.53 380 263 And substantial drop (−27%) of NOx

These results show that the alkanes do not have a significant favorable impact on the particle emissions, whereas the esters and alkanes together are unexpectedly able to very significantly reduce particles more or less proportionally to the ester level (drop of particles of order twice the level of incorporated esters) at the same time as a significant drop of NOx. In this respect, example 5 is very persuasive.

The other parameters (CO, HC) are not degraded. There is even a substantial drop of the CO. By adjusting the levels of esters and alkanes, it is thus possible to optimize emissions from diesel engines. 

1. A mixture intended to supply a boiler or diesel engine comprising: at least one liquid fuel for boiler or a diesel engine fuel chosen among diesel fuel or domestic fuel oil; and at least one biosourced ester where the chain length is included between 8 and 14 carbon atoms incorporated in the fuel; and at least one biosourced alkane where the chain length is included between 8 and 14 carbon atoms, incorporated in the fuel; and wherein the incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture.
 2. The mixture according to claim 1 characterized in that the ester(s) with chain length included between 8 and 14 carbon atoms represent between 5% and 50% of the volume of said mixture.
 3. The mixture according to claim 1, characterized in that the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 5 and 50% by volume of said mixture.
 4. The mixture according to claim 1, characterized in that the incorporated alkane(s) with chain length included between 8 and 14 carbon atoms in the mixture are alkanes obtained by Kolbe electrolysis of volatile fatty acids coming from anaerobic fermentation of biomass or alkanes coming from the biomass by gasification and Fischer-Tropsch synthesis.
 5. The mixture according to claim 1, characterized in that ester(s) with chain length included between 8 and 14 carbon atoms in the mixture are esters in which the acid part is obtained from volatile fatty acids coming from anaerobic biomass fermentation and esterification by an alcohol.
 6. The mixture according to claim 1, characterized in that it comprises at least one additional additive that can improve the cetane number and/or reduce of particle emissions and/or reduce nitrogen oxide emissions by the boiler or diesel engine during operation.
 7. The mixture according to claim 1, characterized in that it comprises at least one additive capable of improving the cold resistance and/or viscosity.
 8. A process for production of a mixture according to claim 1, characterized in that it consists of incorporating in at least one liquid boiler fuel or diesel engine fuel chosen among diesel fuel or domestic fuel oil: at least one biosourced ester where the chain length is included between 8 and 14 carbon atoms; and at least one biosourced alkane where the chain length is included between 8 and 14 carbon atoms; and wherein in a way that the incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture.
 9. A use of a mixture according to claim 1 to supply a boiler or a diesel engine.
 10. The use according to claim 9 in a boiler or diesel engine for reducing the particle emissions during operation of the boiler or engine.
 11. The use according to claim 9 in a boiler or diesel engine for reducing the nitrogen oxide emissions during operation of the boiler or engine.
 12. The use according to claim 9 in a diesel engine for improving the cetane index of the fuel.
 13. The use according to claim 9 in a boiler or diesel engine for wherein other additives are added for improving the cetane number or enhancing the reduction of particle or nitrogen oxide emissions.
 14. The use according to claim 9 in a diesel engine wherein other additives are added for improving the cold resistance and/or viscosity.
 15. The use according to claim 9 in a fixed diesel engine or diesel engine installed in transportation vehicles or boats or worksite heavy equipment or agricultural equipment or small domestic equipment. 